How to Change the Oil in a 2013 Yamaha YZ85 – Step-by-Step Guide

Shop parts for a 2013 Yamaha YZ85 Dirt Bike.

Changing the oil in your 2013 Yamaha YZ85 is crucial for maintaining its performance and longevity. This dirt bike uses a simple two-stroke engine and requires a gear oil change rather than traditional engine oil. Here’s a proprietary MotoSport.com expert guide including all tools needed, step-by-step instructions, and specific callouts for your model.

Tools and Materials Needed

  • 10 mm socket or wrench (for the drain bolt)
  • Drain pan or oil catcher
  • Rubber gloves (for cleanliness and protection)
  • Clean rags or shop towels
  • Measuring cup (graduated, for precise oil measurement)
  • 500 ml (approximately 0.53 US quarts) of recommended transmission oil (consult your manual or use a high-quality 2-stroke gear oil)
  • Replacement crush washer (optional, but recommended if the old one is deformed)
  • Funnel (helps avoid spills during refill)

Preparation Steps

  • Clean the bike: Always start by cleaning around the engine, especially the drain bolt area and fill cap. Dirt or debris can fall into the crankcase during an oil change if not properly cleaned first

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  • Warm up the engine: Run the engine for a few minutes to help the oil flow more freely during draining. Do not get the engine hot; a minute or two is enough

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  • Place the bike on a stand: Use a lift stand or steady crate to keep the bike level and upright.
  • Put on gloves: Protective gloves keep your hands clean and safe from chemicals

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Oil Draining Steps

  • Locate the drain bolt: On the YZ85, the oil drain plug is a 10 mm bolt found below and beside the brake lever area, under the engine case

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  • Place your drain pan: Position the oil catcher under the drain bolt to collect old oil

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  • Remove the fill cap: Unscrew the fill cap on top of the case. This allows air to enter and helps the oil drain more smoothly

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  • Loosen and remove the drain bolt: Use the 10 mm wrench or socket to loosen, then unscrew by hand. Be careful as oil may drain quickly once removed

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  • Let all oil drain: Allow sufficient time until the draining slows to a drip. To get extra oil out, you can lean the bike gently from side to side

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  • Inspect the oil and drain bolt: Check the oil for unusual color (milky, contaminated) and inspect the drain bolt for metal shavings or damage. Clean the bolt and fit a new crush washer if needed

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Reinstallation Steps

  • Install the drain bolt: Once drained, clean around the drain hole, reinsert the bolt (with fresh or existing washer), and tighten snugly but do not over-tighten to avoid stripping threads. Use your wrench for a firm hand-tight finish

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Refilling Steps

  • Measure fresh oil: The 2013 YZ85 takes 500 milliliters (ml) of transmission/gear oil. Carefully measure this amount with a graduated cup

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  • Pour in new oil: Using a funnel, pour the pre-measured oil into the fill hole on the right side of the engine case

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  • Replace the fill cap: Wipe away any spill and screw the cap back on securely

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Final Steps

  • Clean up: Wipe any oil spills, remove the drain pan, and clean tools and work area.
  • Start the engine: Briefly run the bike to allow the oil to lubricate the gearbox. Check for oil leaks around the drain bolt area

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  • Dispose of oil properly: Take old oil to a recycling facility or designated disposal location.

2013 Yamaha YZ85 Model-Specific Callouts

  • Oil quantity is specific: The YZ85 (all recent model years) uses 500 ml of gear oil per change. Using too little or too much can harm the transmission’s performance and longevity

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  • No oil sight glass: The YZ85 does NOT have a sight glass or dipstick, so precise measuring is necessary for correct fill levels

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  • Drain bolt location: The drain bolt is always 10 mm and positioned under the brake area, but it’s easy to mistake engine case bolts for the drain plug—consult your manual if uncertain.
  • Oil recommendation: Yamaha recommends a high-quality transmission/gear oil suitable for 2-stroke motocross bikes. Choose oils like Motul Transoil 10W-30 or equivalent.
  • Check for contaminants: If the drained oil is milky or has excessive shavings, this may indicate water intrusion or premature wear and should be addressed immediately.
  • Copper crush washer: Replace the copper washer on the drain plug periodically to prevent leaks.

Conclusion

The process for changing the oil in a 2013 Yamaha YZ85 is straightforward and great for home mechanics. Following the guidelines above will help keep your dirt bike’s transmission running smoothly and your rides trouble-free. For more OEM parts, fluids, or expert service advice, visit MotoSport.com—your authority for motocross maintenance and performance.

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Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your motorcycle's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.